The present invention relates to hot melt adhesive compositions, and more particularly to a polybutylene based hot melt adhesive which finds utility in nonwoven disposable absorbent articles such as diapers.
Numerous types of nonwoven disposable absorbent articles are commercially available, and are manufactured for use in the absorption and containment of bodily waste such as urine and feces. Typical of such articles are disposable diapers for infants, and undergarments for incontinent adults. Hot melt adhesives are typically used in the construction of such disposable articles.
While a wide range of hot melt adhesive compositions are known and used in the construction of disposable articles, it is also well known that a hot melt adhesive used for bonding in a particular use or application may be completely unsuitable for other uses or applications. Thus, various hot melt adhesive compositions are used in the construction of disposable articles. For example, it is well known that polyolefin based hot melt adhesives are suitable for the construction of diapers, particularly in the bonding of polyethylene films, or the like, to tissue or nonwoven substrates in the production of such articles. However, it is also known that polyolefin based hot melt adhesives are not suitable for bonding of the elastic bands in the diapers because the application characteristics, e.g. sprayability, of polyolefin based adhesives is undesirable for such an application. For this reason, hot melt adhesives based on styrenic block copolymers such as styrene-isoprene-styrene (SIS) block copolymers or styrene-butadiene-styrene (SBS) block copolymers are used for elastic attachment applications. These styrenic block copolymer adhesives, however, also possess shortcomings such as viscosity instability which manifests itself at elevated temperature.
More importantly, the shortcomings of conventional SIS and SBS based hot melt adhesives are particularly manifested in nonwoven applications which require seaming, such as the attachment of elastic side panels to diapers, or adhering of functional attachments such as fastening tape to disposable diapers. Oftentimes such components are required to function at body temperature under high peel stress and/or high shear stress for long periods of time. In such instances, the peel strength and shear strength of conventional adhesives are insufficient. As a result, such applications typically required mechanical bonding, such as ultrasonic welding or a combination of mechanical bonding with an adhesive assist. The equipment used in such applications, however, is often costly requires frequent maintenance, and can limit line speed.